Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$167.84	11.186%	$186.6146	$186.61	$186.60	$186.60
Purchase #2	$192.81	11.828%	$215.6156	$215.62	$215.60	$215.60
Purchase #3	$120.48	8.754%	$131.0268	$131.03	$131.05	$131.00
Purchase #4	$217.39	11.464%	$242.3116	$242.31	$242.30	$242.30
Purchase #5	$241.33	9.409%	$264.0367	$264.04	$264.05	$264.00
Purchase #6	$72.79	8.324%	$78.849	$78.85	$78.85	$78.80
Purchase #7	$232.90	7.542%	$250.4653	$250.47	$250.45	$250.50
7 purchase totals =	$1,245.54		$1,368.9196	$1,368.93	$1,368.90	$1,368.80